1. Field of the Invention
The present invention relates to a control valve unit for failure diagnosis of an evaporation purge system that conveys fuel evaporation from a fuel tank to a carbon canister via an evaporation passage. The unit supplies the fuel evaporation captured by the carbon canister into an intake passage of an internal combustion engine via a purge passage having a purge control valve.
2. Description of the Related Art
Many evaporation purge systems are known. Such purge systems convey fuel evaporation from a fuel tank to a carbon canister via an evaporation passage and supply the fuel evaporation captured by the carbon canister into an intake passage of an internal combustion engine via a purge passage having a purge control valve.
An example of such evaporation purge systems is illustrated in FIG. 7. A vent passage 41 extending from a carbon canister 40 comprises a diagnosis control valve 42, an air cleaner 43, a check valve 44, and pipes 45, 46, 47, such as hoses, which connect adjacent units in series fashion. The diagnosis control valve 42 comprises an on-off valve and is operated for failure diagnosis of the evaporation purge system. The air cleaner 43 blocks dirt and dust when air is introduced through the vent passage 41. The check valve 44 is opened to draw in clean air from, for example, the trunk compartment, and to release pressure from the carbon canister 40 to the outside via, for example, a tire housing or a cross member.
However, because the carbon canister 40, the diagnosis control valve 42, the air cleaner 43 and the check valve 44 are connected in series by the pipes 45, 46 and 47, this known arrangement is costly and requires a large space and many man hours for installation.